The following Hebrew blessing may be said in gratitude to HaShem for giving strength to those who are weary (either weary of heart or of body):

The Hebrew greeting Yasher Koach! means "May your strength be firm," and is often said to those who have had performed Torah reading aliyah at synagogue or to those whom you wish to commend for a job well done (e.g., "I'd like to say Yasher Koach to our students").

(This expression is similar to the congregational exclamation "Chazak Chazak venit-chazek" ("Strong, strong, and let us be strengthened!") that follows the conclusion of each of the five books of the Torah.)

"Hast thou not known? hast thou not heard, that the everlasting God, the LORD, the Creator of the ends of the earth, fainteth not, neither is weary? there is no searching of his understanding. He giveth power to the faint; and to them that have no might he increaseth strength. Even the youths shall faint and be weary, and the young men shall utterly fall: But they that wait upon the LORD shall renew their strength; they shall mount up with wings as eagles; they shall run, and not be weary; and they shall walk, and not faint."

Isaiah 40:28-31

נתֵן לַיָּעֵף כּחַ וּלְאֵין אוֹנִים עָצְמָה יַרְבֶּה

no-ten la-ya-eif ko-ach, ul-ein o-nim otz-mah yar-beh

"He gives power (ko'ach) to the faint,and to him who has no might he increases strength"(Isa. 40:29)

Note that the word translated "strength" in this verse (otzmah) comes from the same root for "bones" (עֲצָמוֹת). This alludes to the vision of the "dry bones" being clothed with life at the time of resurrection. "Thus says the Lord God to these bones: 'Behold, I will cause breath to enter you, and you shall live'" (Ezek. 37:5). If God has the power to give life to dessicated bones, surely his resurrection power can "quicken us" through the life of our beloved Savior Yeshua who said, "You will receive power (i.e., koach:כּחַ) when the Holy Spirit has come upon you, and you will be my witnesses" (Acts 1:7). Therefore we can recite the Hebrew blessing, בָּרוּךְ אַתָּה יהוה אֳלהֵינוּ מֶלֶךְ הָעוֹלָם הַנוֹתֵן לַיָּעֵף כּח, "Blessed are You, L-rd our G-d, King of the Universe, who gives strength to the weary." We find real everlasting strength in our Comforter, the One who gives us life...